Application of specific electrical fields to spinal nerve roots, the spinal cord, and/or other nerve bundles for the purpose of chronic pain management has been actively practiced since the 1960s. While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of an electrical field to spinal nervous tissue (i.e., spinal nerve roots and spinal cord bundles) can effectively interfere with the transmission of certain pain signals through such nervous tissue. More specifically, applying particularized electrical pulses to spinal nervous tissue that corresponds to regions of the body afflicted with chronic pain can induce paresthesia, or a subjective sensation of numbness or tingling, in the pain-afflicted regions. Depending on the individual patient, paresthesia can effectively “mask” certain pain sensations to the brain.
The above description uses the term “particularized” to denote that the applied electrical energy is intended to be focused on the specific spinal nervous tissue associated with the afflicted bodily regions. Care should be taken to avoid over stimulating the targeted nervous tissue, as over stimulation could lead to paresthesia being perceived in non-afflicted regions or, alternatively, feelings of discomfort.
As a first step to delivering effective electrical energy to targeted nervous tissue, the source of the electrical energy must be positioned proximate to such nervous tissue. Electrical energy is commonly delivered through conductive electrodes positioned external to a patient's dura layer, a structure that surrounds the spinal cord. Electrodes are carried by two primary vehicles: the percutaneous catheter and the laminotomy lead. Percutaneous catheters and laminotomy leads will be collectively referred to as “stimulation leads.”
Percutaneous catheters, or percutaneous leads, commonly have two or more electrodes (for example, two, four, and eight) and are positioned above the dura layer through the use of a Touhy-like needle that passes through the skin, between desired vertebrae, and opens above the dura layer. Laminotomy leads have a thin paddle configuration and typically possess a plurality of electrodes (for example, two, four, eight, or sixteen) arranged in one or more columns. Surgical intervention is required for implanting laminotomy leads. In particular, a partial laminectomy is required, which involves the resection and removal of certain vertebral tissue to allow both access to the dura and proper positioning of the laminotomy lead.
Assuming that physical placement of the electrical energy source can be achieved, specific “selection” of the targeted nervous tissue from an encompassing tissue bundle is achieved through refinement of the delivered electrical energy. To this end, the delivered electrical energy is defined by an electrode configuration and an electric pulse waveform, or collectively a “stimulation setting.”
The overall form of the delivered electrical energy is defined by the polarity of each electrode of the stimulation lead. With modern stimulation systems, each electrode can assume a positive polarity (an anode), a negative polarity (a cathode), or an off-state. The collective definition of the polarities of each electrode of a stimulation lead is described as an “electrode configuration.”
The electric pulse waveform defines the nature of the signal delivered through the active electrodes. Of course, an electric pulse waveform is defined by a plurality of variables, including: pulse width (μs) (i.e., the duration in which the pulse is in a high state), frequency (Hz), amplitude (V), and sometimes phase (i.e., mono-phasic or bi-phasic). For purposes of description, a collection of these variables to define a single waveform will be referred to as a “treatment parameter set.”
Identifying an optimum stimulation setting-one that masks a maximum quantity of pain with minimum over stimulation-can be time consuming and difficult. In particular, not even considering the endless combinations that can be effected by modifying the variables of a treatment parameter set, an eight-electrode stimulation lead offers 6,050 possible electrode combinations.
As may be understood from the above description, a single stimulation setting corresponds to a single treatment parameter set and a single electrode configuration. Consequently, each stimulation setting typically addresses only a single localized region of the body. If a patient experiences complex pain (i.e., pain that extends across multiple or varied regions of the body), then multiple stimulation settings may be required to address such pain. Further yet, different stimulation settings may be required for different times of the day or for different activities within the day, whereas changes in body position (e.g., lying down, sitting, standing) may impair or alter the effectiveness of any one stimulation setting.
FIG. 1 illustrates a modern, radio frequency (RF) stimulation system 1000. In particular, the system 1000 includes an external transmitter 1002 that is connected to an antenna 1004. Internally, a receiver 1008 is connected to at least one stimulation lead 1010 (and 1012), which in this instance is illustrated having eight electrodes 1010a–h (and 1012a–h for stimulation lead 1012). The receiver 1008 Bib communicates, via an antenna 1006, with the transmitter 1002 through the skin 1032 of a patient.
Stimulation settings are stored within a memory of the transmitter 1002. Stimulation settings can be programmed into the transmitter 1002 using transmitter-based controls (not shown) or using a computer 1028 (e.g., U.S. Pat. No. 5,938,690 to Law et al.) through a removable connection 1030. operatively, stimulation settings are imposed on a RF carrier signal and passed to the receiver 1008 through the skin 1032 to effect stimulation through electrodes 1010a–h and 1012a–h. 
The system 1000 allows the storage and application of 1–24 stimulation settings. Each stimulation setting is numerically represented (i.e., “1”, “2”, “3”, etc.) based on an order of input into the transmitter 1002. The transmitter 1002 executes all stored stimulation settings sequentially, based on the settings respective numerical representations. The execution of “adjacent” stimulation settings is made within a fixed time interval, such interval being of such a duration that switching between adjacent stimulation settings is largely imperceivable to the patient.
To this end, the conventional system would enable up to 24 different pain areas to be addressed. However, short of reprogramming the stored stimulation settings, this system does not readily allow changes in stimulation settings for changes in activities or patient posture. Moreover, with each stimulation setting being simply represented by an alphanumeric representation, a patient or practitioner must maintain a separate log that correlates each stimulation setting with its stimulation effect. Otherwise, the patient would be required to execute each stored stimulation setting to appreciate its consequence.
Accordingly, a need exists for a stimulation system that provides a user substantive information regarding the effects or intended application of a stored stimulation setting.
A further need exists for a stimulation system that allows stored stimulation settings to be both readily and arbitrarily grouped, whereas each stimulation setting of a group is directed to addressing a common condition, and multiple groups are available for execution.